For example, a method called “GS (Gate Shift)-GB (Gate Block)-CBT (Circuit Breaker Trip)” is used for the protective stop of a separately-excited power conversion device using a thyristor element. In a direct current power transmission method such as HVDC (High Voltage Direct Current), etc., there are cases where the power conversion device is stopped using “GS-GB-CBT” when the control device generating the gate pulses fails. GS causes the power conversion device to operate in an inverter region by setting the trigger phase of the thyristor to be 90° or more. GB is the stopping of the gate pulses. CBT is the opening of a circuit breaker connected to the alternating current side of the power conversion device. “GS-GB-CBT” is the series of protective interlocking of performing GS, subsequently performing GB, and further performing CBT. Also, there is a method in which the protective stop is performed using BPP (bypass pairs) instead of GS. BPP causes the high-voltage-side arms and the low-voltage-side arms of the converter arms of the power converter that are connected to the same phase to conduct simultaneously.
Although the GS interval generally is about 40 ms to 100 ms, for example, when a failure occurs such as when a control power supply of a control device is lost, power interruption compensation is performed until the GS interval is completed. The power interruption compensation is performed to maintain the gate pulse generation ability of the control device so that the protective interlocking is completed for the power conversion device as an entirety. To this end, the control device of the power conversion device includes power interruption compensation circuits for a subdivided control circuit. For example, for the configuration of a twelve-phase power conversion device including twelve converter arms (valves), a control circuit that generates the gate pulse is provided for each arm of the twelve-phases. That is, a power interruption compensation circuit is provided for each phase of the twelve-phases. Therefore, the circuit configuration is complex; and the control device is larger. It is desirable to simplify the circuit configuration of such a control device.